Batteries are commonly used as electrical energy sources. A battery contains a negative electrode, typically called the anode, and a positive electrode, typically called the cathode. The anode contains an active material that can be oxidized. The cathode contains an active material that can be reduced. The anode active material is capable of reducing the cathode active material.
When a battery is used as an electrical energy source in a device, electrical contact is made to the anode and the cathode, allowing electrons to flow through the device and permitting the respective oxidation and reduction reactions to occur to provide electrical power. An electrolyte in contact with the anode and the cathode contains ions that flow through the separator between the electrodes to maintain charge balance throughout the battery during discharge.
In a metal air electrochemical cell, oxygen is reduced at the cathode, and a metal, such as zinc, is oxidized at the anode. Oxygen is supplied to the cathode from the atmospheric air external to the cell through air access ports in the battery housing. Metal oxide, such as zinc oxide or a zincate salt, is formed in the anode. Thus, the overall electrochemical reaction within a zinc-air electrochemical cell results in zinc metal being oxidized to zinc oxide or zincate ions and oxygen from the air being reduced to hydroxyl ions. While these chemical reactions are taking place, electrons are transferred from the anode to the cathode thereby providing power to the device.